Not all saturated fats increase the chances of developing diabetes and some could help protect against the disease, a study has shown.

The kind of saturated fat found in dairy products such as yoghurt is likely to reduce the risk of type 2 diabetes, say scientists.

But other types obtained from red meat and fried food, or generated after consuming carbohydrates or alcohol, may be harmful.

The differences depend on the number of carbon atoms saturated fatty acid molecules contain, according to the research.

Those with an even number of carbon atoms were associated with a higher risk of type 2 diabetes, the most common form of the disease affecting almost three million people in the UK.

Molecules with odd numbers of carbon atoms led to a protective effect.

Saturated fat is found in animal products such as butter, cheese and red meat.

It is generally considered unhealthy and linked to high levels of cholesterol and heart disease, as well as type 2 diabetes.

Lead researcher Dr Nita Forouhi, from the Medical Research Council Epidemiology Unit at Cambridge University, said: "Our findings provide strong evidence that individual saturated fatty acids are not all the same. The challenge we face now is to work out how the levels of these fatty acids in our blood correspond to the different foods we eat.

"Our research could help trigger new directions in experimental studies and basic research so we can better understand the biology."

She added: "These odd-chain saturated fatty acids are well-established markers of eating dairy fats, which is consistent with several recent studies, including our own, that have indicated a protective effect against type 2 diabetes from eating yoghurt and other dairy products.

"In contrast, the situation for even-chain saturated fatty acids is more complex. As well as being consumed in fatty diets, these blood fatty acids can also be made within the body through a process which is stimulated by the intake of carbohydrates and alcohol."

The Epic-InterAct study, funded by the European Commission, investigated the relationship between blood levels of nine different saturated fatty acids and type 2 diabetes risk.

Researchers looked at 12,403 people who developed the disease from a population of more than 340,000 from eight European countries.

Levels of each of the nine fatty acids in participants' bloodstreams were compared with type 2 diabetes incidence.

The findings appear in the journal The Lancet Diabetes and Endocrinology.

Professor Nick Wareham, chief coordinator of the InterAct project to identify genetic and lifestyle diabetes risk factors, said: "With the world's largest study of its kind, we can place a lot of confidence in these findings, which help us to better understand the relationships between saturated fatty acids and risk of developing diabetes."

Type 2 diabetes, linked in 90% of cases to overweight and obesity, is soaring. New research shows 40% of Americans and 50% of Hispanics and non-Hispanic black women will get the disease at some point in their life and the numbers are unlikely to be much different elsewhere in the developed world